Make struct Lisp_Objfwd etc. objects read-only

Initialize these objects statically, and make them constants.
This is a bit safer and more efficient.
* src/data.c (XBOOLFWD, XKBOARD_OBJFWD, XFIXNUMFWD, XOBJFWD):
* src/lisp.h (XBUFFER_OBJFWD):
Return a pointer-to-const instead of an unrestricted pointer.
(lispfwd): fwdptr is now a pointer-to-const instead of an
unrestricted pointer.  All uses changed.
(SET_SYMBOL_FWD): Accept pointer-to-const instead of an
unrestricted pointer.
(DEFVAR_LISP, DEFVAR_LISP_NOPRO, DEFVAR_BOOL, DEFVAR_INT)
(DEFVAR_KBOARD): Initialize static structures statically
instead of dynamically, and make them const.
* src/lread.c (defvar_int, defvar_bool, defvar_lisp_nopro)
(defvar_lisp, defvar_kboard): Accept pointer-to-const instead
of an unrestricted pointer; it’s now the caller’s
responsibility to initialize the pointed-to storage.  No need
for a separate address argument any more.  All callers
changed.

3 files changed, 40 insertions, 53 deletions

diff --git a/src/data.c b/src/data.c
index 936bb74f69a..11cd598ed85 100644
--- a/src/data.c
+++ b/src/data.c
@@ -62,25 +62,25 @@ OBJFWDP (lispfwd a)
   return XFWDTYPE (a) == Lisp_Fwd_Obj;
 }
 
-static struct Lisp_Boolfwd *
+static struct Lisp_Boolfwd const *
 XBOOLFWD (lispfwd a)
 {
   eassert (BOOLFWDP (a));
   return a.fwdptr;
 }
-static struct Lisp_Kboard_Objfwd *
+static struct Lisp_Kboard_Objfwd const *
 XKBOARD_OBJFWD (lispfwd a)
 {
   eassert (KBOARD_OBJFWDP (a));
   return a.fwdptr;
 }
-static struct Lisp_Intfwd *
+static struct Lisp_Intfwd const *
 XFIXNUMFWD (lispfwd a)
 {
   eassert (INTFWDP (a));
   return a.fwdptr;
 }
-static struct Lisp_Objfwd *
+static struct Lisp_Objfwd const *
 XOBJFWD (lispfwd a)
 {
   eassert (OBJFWDP (a));
diff --git a/src/lisp.h b/src/lisp.h
index 62c3230a148..a0a7cbdf518 100644
--- a/src/lisp.h
+++ b/src/lisp.h
@@ -803,7 +803,7 @@ INLINE void
    union of the possible values (struct Lisp_Objfwd, struct
    Lisp_Intfwd, etc.).  The pointer is packaged inside a struct to
    help static checking.  */
-typedef struct { void *fwdptr; } lispfwd;
+typedef struct { void const *fwdptr; } lispfwd;
 
 /* Interned state of a symbol.  */
 
@@ -2204,7 +2204,7 @@ SET_SYMBOL_BLV (struct Lisp_Symbol *sym, struct Lisp_Buffer_Local_Value *v)
   sym->u.s.val.blv = v;
 }
 INLINE void
-SET_SYMBOL_FWD (struct Lisp_Symbol *sym, void *v)
+SET_SYMBOL_FWD (struct Lisp_Symbol *sym, void const *v)
 {
   eassume (sym->u.s.redirect == SYMBOL_FORWARDED && v);
   sym->u.s.val.fwd.fwdptr = v;
@@ -2759,7 +2759,7 @@ struct Lisp_Kboard_Objfwd
 INLINE enum Lisp_Fwd_Type
 XFWDTYPE (lispfwd a)
 {
-  enum Lisp_Fwd_Type *p = a.fwdptr;
+  enum Lisp_Fwd_Type const *p = a.fwdptr;
   return *p;
 }
 
@@ -2769,7 +2769,7 @@ BUFFER_OBJFWDP (lispfwd a)
   return XFWDTYPE (a) == Lisp_Fwd_Buffer_Obj;
 }
 
-INLINE struct Lisp_Buffer_Objfwd *
+INLINE struct Lisp_Buffer_Objfwd const *
 XBUFFER_OBJFWD (lispfwd a)
 {
   eassert (BUFFER_OBJFWDP (a));
@@ -3096,11 +3096,11 @@ enum maxargs
    CALLN is overkill for simple usages like 'Finsert (1, &text);'.  */
 #define CALLN(f, ...) CALLMANY (f, ((Lisp_Object []) {__VA_ARGS__}))
 
-extern void defvar_lisp (struct Lisp_Objfwd *, const char *, Lisp_Object *);
-extern void defvar_lisp_nopro (struct Lisp_Objfwd *, const char *, Lisp_Object *);
-extern void defvar_bool (struct Lisp_Boolfwd *, const char *, bool *);
-extern void defvar_int (struct Lisp_Intfwd *, const char *, intmax_t *);
-extern void defvar_kboard (struct Lisp_Kboard_Objfwd *, const char *, int);
+extern void defvar_lisp (struct Lisp_Objfwd const *, char const *);
+extern void defvar_lisp_nopro (struct Lisp_Objfwd const *, char const *);
+extern void defvar_bool (struct Lisp_Boolfwd const *, char const *);
+extern void defvar_int (struct Lisp_Intfwd const *, char const *);
+extern void defvar_kboard (struct Lisp_Kboard_Objfwd const *, char const *);
 
 /* Macros we use to define forwarded Lisp variables.
    These are used in the syms_of_FILENAME functions.
@@ -3121,29 +3121,34 @@ extern void defvar_kboard (struct Lisp_Kboard_Objfwd *, const char *, int);
 
 #define DEFVAR_LISP(lname, vname, doc)          \
   do {                                          \
-    static struct Lisp_Objfwd o_fwd;            \
-    defvar_lisp (&o_fwd, lname, &globals.f_ ## vname);          \
+    static struct Lisp_Objfwd const o_fwd       \
+      = {Lisp_Fwd_Obj, &globals.f_##vname};     \
+    defvar_lisp (&o_fwd, lname);                \
   } while (false)
 #define DEFVAR_LISP_NOPRO(lname, vname, doc)    \
   do {                                          \
-    static struct Lisp_Objfwd o_fwd;            \
-    defvar_lisp_nopro (&o_fwd, lname, &globals.f_ ## vname);    \
+    static struct Lisp_Objfwd const o_fwd       \
+      = {Lisp_Fwd_Obj, &globals.f_##vname};     \
+    defvar_lisp_nopro (&o_fwd, lname);          \
   } while (false)
 #define DEFVAR_BOOL(lname, vname, doc)          \
   do {                                          \
-    static struct Lisp_Boolfwd b_fwd;           \
-    defvar_bool (&b_fwd, lname, &globals.f_ ## vname);          \
+    static struct Lisp_Boolfwd const b_fwd      \
+      = {Lisp_Fwd_Bool, &globals.f_##vname};    \
+    defvar_bool (&b_fwd, lname);                \
   } while (false)
 #define DEFVAR_INT(lname, vname, doc)           \
   do {                                          \
-    static struct Lisp_Intfwd i_fwd;            \
-    defvar_int (&i_fwd, lname, &globals.f_ ## vname);           \
+    static struct Lisp_Intfwd const i_fwd       \
+      = {Lisp_Fwd_Int, &globals.f_##vname};     \
+    defvar_int (&i_fwd, lname);                 \
   } while (false)
 
 #define DEFVAR_KBOARD(lname, vname, doc)                        \
   do {                                                          \
-    static struct Lisp_Kboard_Objfwd ko_fwd;                    \
-    defvar_kboard (&ko_fwd, lname, offsetof (KBOARD, vname ## _)); \
+    static struct Lisp_Kboard_Objfwd const ko_fwd               \
+      = {Lisp_Fwd_Kboard_Obj, offsetof (KBOARD, vname##_)};     \
+    defvar_kboard (&ko_fwd, lname);                             \
   } while (false)
 
 
diff --git a/src/lread.c b/src/lread.c
index dd35cf9063e..5f33fcd6957 100644
--- a/src/lread.c
+++ b/src/lread.c
@@ -4425,28 +4425,19 @@ defalias (struct Lisp_Subr *sname, char *string)
    C variable of type intmax_t.  Sample call (with "xx" to fool make-docfile):
    DEFxxVAR_INT ("emacs-priority", &emacs_priority, "Documentation");  */
 void
-defvar_int (struct Lisp_Intfwd *i_fwd,
-            const char *namestring, intmax_t *address)
+defvar_int (struct Lisp_Intfwd const *i_fwd, char const *namestring)
 {
-  Lisp_Object sym;
-  sym = intern_c_string (namestring);
-  i_fwd->type = Lisp_Fwd_Int;
-  i_fwd->intvar = address;
+  Lisp_Object sym = intern_c_string (namestring);
   XSYMBOL (sym)->u.s.declared_special = true;
   XSYMBOL (sym)->u.s.redirect = SYMBOL_FORWARDED;
   SET_SYMBOL_FWD (XSYMBOL (sym), i_fwd);
 }
 
-/* Similar but define a variable whose value is t if address contains 1,
-   nil if address contains 0.  */
+/* Similar but define a variable whose value is t if 1, nil if 0.  */
 void
-defvar_bool (struct Lisp_Boolfwd *b_fwd,
-             const char *namestring, bool *address)
+defvar_bool (struct Lisp_Boolfwd const *b_fwd, char const *namestring)
 {
-  Lisp_Object sym;
-  sym = intern_c_string (namestring);
-  b_fwd->type = Lisp_Fwd_Bool;
-  b_fwd->boolvar = address;
+  Lisp_Object sym = intern_c_string (namestring);
   XSYMBOL (sym)->u.s.declared_special = true;
   XSYMBOL (sym)->u.s.redirect = SYMBOL_FORWARDED;
   SET_SYMBOL_FWD (XSYMBOL (sym), b_fwd);
@@ -4459,37 +4450,28 @@ defvar_bool (struct Lisp_Boolfwd *b_fwd,
    gc-marked for some other reason, since marking the same slot twice
    can cause trouble with strings.  */
 void
-defvar_lisp_nopro (struct Lisp_Objfwd *o_fwd,
-                   const char *namestring, Lisp_Object *address)
+defvar_lisp_nopro (struct Lisp_Objfwd const *o_fwd, char const *namestring)
 {
-  Lisp_Object sym;
-  sym = intern_c_string (namestring);
-  o_fwd->type = Lisp_Fwd_Obj;
-  o_fwd->objvar = address;
+  Lisp_Object sym = intern_c_string (namestring);
   XSYMBOL (sym)->u.s.declared_special = true;
   XSYMBOL (sym)->u.s.redirect = SYMBOL_FORWARDED;
   SET_SYMBOL_FWD (XSYMBOL (sym), o_fwd);
 }
 
 void
-defvar_lisp (struct Lisp_Objfwd *o_fwd,
-             const char *namestring, Lisp_Object *address)
+defvar_lisp (struct Lisp_Objfwd const *o_fwd, char const *namestring)
 {
-  defvar_lisp_nopro (o_fwd, namestring, address);
-  staticpro (address);
+  defvar_lisp_nopro (o_fwd, namestring);
+  staticpro (o_fwd->objvar);
 }
 
 /* Similar but define a variable whose value is the Lisp Object stored
    at a particular offset in the current kboard object.  */
 
 void
-defvar_kboard (struct Lisp_Kboard_Objfwd *ko_fwd,
-               const char *namestring, int offset)
+defvar_kboard (struct Lisp_Kboard_Objfwd const *ko_fwd, char const *namestring)
 {
-  Lisp_Object sym;
-  sym = intern_c_string (namestring);
-  ko_fwd->type = Lisp_Fwd_Kboard_Obj;
-  ko_fwd->offset = offset;
+  Lisp_Object sym = intern_c_string (namestring);
   XSYMBOL (sym)->u.s.declared_special = true;
   XSYMBOL (sym)->u.s.redirect = SYMBOL_FORWARDED;
   SET_SYMBOL_FWD (XSYMBOL (sym), ko_fwd);